Optical system manufacturing and alignment system

ABSTRACT

An optical component manipulation system has two opposed jaws, which can each be independently positioned relative to each other in a coordinate plane to thereby effect the desired positioning of optical components within the larger system. Z-axis rigidity is provided by air-bearings. Laser heating of the jaws is used for solder, or similar heat driven bonding, processes.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 09/667,186filed on Sep. 21, 2000 which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Component alignment is of critical importance in semiconductor and/orMEMS (micro electro-mechanical systems) based optical systemmanufacturing. The basic nature of light requires that light generating,transmitting, and modifying components must be positioned accuratelywith respect to one another, especially in the context offree-space-optical systems, in order to function properly andeffectively in electro-optical or all optical systems. Scalescharacteristic of semiconductor and MEMS can necessitate micron tosub-micron alignment accuracy.

Consider the specific example of coupling a semiconductor diode laser,such as a pump or transmitter laser, to a fiber core of a single modefiber. Only the power that is coupled into the fiber core is usable. Thecoupling efficiency is highly dependent on accurate alignment betweenthe laser output facet and the core; inaccurate alignment can result inpartial or complete loss of signal transmission through the opticalsystem.

Other more general examples include optical amplification, receivingand/or processing systems. Some alignment is typically required betweenan optical signal source, such as the fiber endface, and a detector. Inmore complex systems, including tunable filters, for example, alignmentis required not only to preserve signal power but also to yield highquality or high finesse systems through the suppression of undesirableoptical modes within and without the systems.

Generally, there are two types of alignment strategies: active andpassive. Typically in passive alignment of the optical components,registration or alignment features are fabricated directly on thecomponents or component carriers as well as on the platform to which thecomponents are to be mounted. The components are then mounted and bondeddirectly to the platform using the alignment features. In activealignment, an optical signal is transmitted through the components anddetected. The alignment is performed based on the transmissioncharacteristics to enable the highest possible performance level for thesystem.

In the context of commercial volume manufacturing, selection betweenactive and passive alignment, or some mix of the two, is determinedbased on the quality of part needed versus the margins for the part.Lower cost, lower performance devices are typically manufactured withentirely passive alignment strategies, whereas the manufacture of highperformance devices typically involves at least some active alignment.

SUMMARY OF THE INVENTION

There is thus a need in optical system manufacture for the precisemanipulation of optical components relative to the substrate on which,and/or module in which, they are installed. Such manipulation includesthe placement, attachment, and any subsequent positional modification toachieve the specified level of alignment. These needs transcend thespecific classes of alignment strategies: active and passive.

The present invention concerns an optical component manipulation systemthat has two opposed jaws. In the preferred embodiments, each of thesejaws can be independently positioned relative to each other. Further,each jaw may be moved either vertically and/or horizontally to effectthe desired positioning of optical components within the larger system.The optical component may be optical elements that are directly attachedto the substrate or a composite components in which elements that areinstalled on mounting structures, which the system then manipulates.

In general, according to one aspect, the invention features an opticalcomponent manipulation system. This system comprises first and secondopposed jaws. In the typical application, these jaws are used to engageeither side of an optical component to manipulate, such as move,install, place and/or deform, the optical component relative to anoptical substrate, bench, and/or module.

A first x-axis position detection system is used to detect an x-axisposition of the first jaw and a first y-axis position detection systemis used to detect a y-axis position of the first jaw. Similarly, secondx-axis and y-axis position detection systems are used to detect anx-axis and y-axis positions, respectively, of the second jaw.

To manipulate the position of the first jaw along the x- and y-axis,respective first x-axis and y-axis actuator systems are provided forpositioning the first jaw. Similarly, second x-axis and y-axis actuatorsare provided for positioning the second jaw.

In the preferred embodiment, the system further comprises a system frameand first and second air bearings between the jaws and the system frame.These air bearings provide a mechanism for z-axis support of the jaws ina low stiction fashion. More specifically, the air bearings are locatedbetween first and second stages, to which the jaws are rigidly attached,and the system frame. They prevent interfacial adhesion present betweenthe stages at an interface with the system frame.

In one implementation, a heating system is provided for preferably bothof the first and second jaws. This allows the jaws to be heated, in acontrolled fashion, to effect solder bonding, for example. In thepreferred embodiment, the heating system comprises a laser system thatgenerates one or two beams that are focused on the respective jaws toirradiate the jaws and thereby control their temperature.

In the preferred embodiment, the jaws extend downward. This allows thejaws to engage an optical substrate from above and also, in someimplementations, reach into a package in which the substrate or benchhas been installed. Y-axis suspension systems can be used in thisconfiguration to support the stages, and thus the jaws.

In the preferred embodiment, the actuator systems comprise voice coils,although in other implementations, other precision actuator systems areused such as linear motors and/or flexure systems, with or withoutpiezo-electric-based actuators.

In the preferred embodiment, optical encoder/grating systems are usedfor the position detection systems. The gratings are attached to thestages and the encoders are attached to the system frame to providefeedback control to a controller that drives the actuators.

In the preferred embodiment, the stages and jaws have a low mass toprovide for high speed positioning. In some cases, however, it may berequired to add mass to the stage systems for provide for stability.

In general, according to another aspect, the invention can also becharacterized in the context of an optical structure manipulationprocess. This process comprises engaging an optical structure with firstand second jaws. In one embodiment, this engagement occurs serially. Thefirst and second jaws are then actuated, possibly independently, to movethe optical component along x- and y-axes to provide for its precisemanipulation.

The above and other features of the invention including various noveldetails of construction and combinations of parts, and other advantages,will now be more particularly described with reference to theaccompanying drawings and pointed out in the claims. It will beunderstood that the particular method and device embodying the inventionare shown by way of illustration and not as a limitation of theinvention. The principles and features of this invention may be employedin various and numerous embodiments without departing from the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure is a schematic, elevation view of an embodiment of theoptical system alignment system of the present invention in whichsimilar reference characters refer to similar parts. The drawing is notto scale; emphasis has instead been placed upon illustrating theprinciples of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The figure illustrates an optical system alignment system 100, which hasbeen constructed according to the principles of the present invention.

The alignment system 100 comprises a system frame 110. The frameprovides the structural/mechanical support for the mechanical andelectro-mechanical components of the system.

A substrate support frame 114 is rigidly connected to the system frame110. A substrate holder/translator 112 is installed on the substrateframe 114.

The substrate holder/translator 112 mechanically engages a substrate 12.The mechanical engagement is currently in the form of jaws or grippersthat engage the substrate 112 and pull it into rigid engagement with aplatform. Other rigid holding techniques such as a vacuum chuck system,however, are used in other embodiments.

The holder/translator 112 further has the capability to preciselyposition the substrate 12 along the z-axis. (The z-axis extends into thepage in the figure, the x and y axes are as shown.) In one embodiment az-axis actuator, such as a voice coil or linear motor, in combinationwith a position detector, such as an optical encoder, 113 is used toenable precise sub-micron positioning of the substrate along the z-axis.

In operation, the alignment system 100 positions optical components 10over and on the substrate 12. When properly positioned, the alignmentsystem 100 then attaches the optical components 10, in oneimplementation. The modes of permanent attachment can be adhesive/epoxybonding, laser welding, thermocompression, ultrasonic bonding and/orsolder bonding. In this final example, solder preforms or layers 14 areformed on the substrate 12. The optical components, with potentiallytheir own solder layer or attached preform, are then lowered onto thebench 12.

In other operational modes, the substrate 12 is delivered to the machinewith some or all of the optical components 10 already permanently ortemporarily attached to the substrate, and the alignment system 100otherwise manipulates the components 10 relative to the substrate 12and/or each other. For example, the alignment system 100 moves and/orplastically deforms the optical components 10 to achieve properalignment in the context of an optical system formed on the top surfaceof the substrate/bench 12. This alignment is performed actively in oneembodiment with an optical link within the optical system beingactivated by energizing an active element, such as laser diode on thesubstrate, or alternatively by supplying an optical signal from outsidethe optical system or module.

In order to manipulate the optical component 10, the alignment system100 has a left and right opposed jaws 120A, 120B. These jaws extendtowards each other to mechanically engage an optical component 10therebetween. In the preferred embodiment, these jaws are constructedfrom a rigid material that is also thermally stable, such as a metalalloy. In the preferred embodiment, they are constructed from INVAR®material. In other embodiments, the jaws are constructed from a ceramic,for example, which is either an electrical insulator, or alternativelyhas been doped to render the ceramic electrically conductive.

The left and right jaws 120A, 120B are rigidly attached to and supportedby respective left and right stages 122A, 122B. In the preferredembodiment, the left and right stages 122A, 122B are constructed from arigid material. In some implementation, it has a low co-efficient ofthermal expansion to improve the temperature stability of the alignmentsystem 100 overall. In the present embodiment, the stages 122A, 122B areconstructed from a machined aluminum alloy.

The left and right stages 122A, 122B are rigidly supported on the systemframe 110 in the z-axis direction via a low stiction, low friction, lowbacklash interface. In the preferred embodiment, this interface is inthe form of left and right air bearings 124A, 124B. In the illustratedembodiment, the air bearings are round. In possibly a preferredembodiment, the air bearings are square and parallel to the x and y axesto decrease the distance between the tips of the jaws 120A, 120B, whichare under stress, and the support afforded by the air bearings 124A,124B. In either case, this configuration reduces the degrees of freedomavailable to the stages to three, x-axis and y-axis movement androtation around the z-axis or in the direction of angle α.

The left and right stages 122A, 122B are supported vertically, or in thedirection of the y-axis by vertical support systems. In the preferredembodiment, the vertical support is via active (“floater”) systems.Specifically, left and right voice coils systems 162A, 162Belectromagnetically connect the left and right stages 122A, 122B,respectively, to the system frame 110. In the current embodiment, twovoice coil floaters are used for each stage.

As is generally known, these voice coil systems comprise a stator 152and a coil 154. In the current embodiment, the all of the coils 154 arerigidly attached to the stages 122 and the stators 152 are rigidlyattached to the system frame 110. This configuration has the advantageof reducing stage weight at the expense of requiring electrical wiringbetween the frame 110 and the flying stages 122, which results in aforce bias on the stages. In a possibly preferred embodiment, low massstators are installed on the stages 122 to avoid the need for directwiring to the stages 122.

In other embodiments, rather than voice coil systems, other precisionpositioning systems are used such as flexure systems with or withoutpiezoelectric actuators and/or linear motor systems.

Positioning of the left and right stages 122A, 122B and thus therespective jaws 120A, 120B is accomplished via a system of actuators. Inthe preferred embodiment, a y-axis actuator system comprises a set oftwo voice coils for each of the left and right stages 122A, 122B.Specifically, in the context of the left stage 122A, a left y-axisactuator system comprises a first y-axis voice coil 160A and a secondy-axis voice coil 164A.

As discussed previously, in the preferred embodiment, the stator 152 ofeach of these y-axis voice coils 160, 164 is connected to the systemframe 110 and the coils are connected to the stages 122.

The first and second y-axis voice coils 160, 164 are controlled by asystem controller 210 via an amplifier bank 200 to vertically position,or position along one axis, the stages 122 and corresponding jaws 120.

In the present embodiment, two y-axis voice coils 160, 164 are driven intandem so that the stages 122A, 122B move, but parallel to the x-axisand y-axis. In a current implementation, the voice coils 164A and 164Bare driven to position the respective stages and voice coils 160A, 160Bare driven to prevent stage rotation or suppress stage rotation aroundthe z-axis.

In alternative embodiments, the first and second voice coils 160, 164are driven differentially to rotate the stages 122A, 122B around thez-axis or in the direction of angle α to thereby add a further degree offreedom in the movement in the respective jaws 120A, 120B.

In order to provide closed-loop control of the vertical position of thestages 122A, 122B and consequently the left and right jaws 120A, 120B,y-axis position is detected. Each stage 122 is provided with a y-axisposition detection system. For example, in the context of the left stage122A, the y-axis position detection system comprises a position encodersystem. Specifically, in the preferred embodiment, optical encoderscheme is used, which comprises a grating 126A, which is attached to thestage 122A, and an optical detector 128A that reads the markings on thegrating 126A. The optical detectors 128 are connected rigidly eitherdirectly or indirectly to the system frame 110 to detect y-axis movementof the respective stage 122.

In the current implementation, the y-axis position detection systemfurther comprises a second set of y-axis position encoders comprisinggratings 136 and encoders 138 for each stage. The second set of encodersis used to provide the feedback necessary to prevent or at least controlstage rotation.

Each of the left and right stages 122A, 122B is further provided withx-axis actuators for positioning the left and right stages along thex-axis, and thus, position the corresponding left and right jaws 120A,120B. In the preferred embodiment, these x-axis actuator systemscomprise voice coil systems.

In alternative embodiments, linear motor and/or flexure actuator systemsare implemented in place of the voice coils.

Specifically, in the context of the left stage 122A, the x-axis actuatorcomprises a voice coil 150A.

Closed loop control of the x-axis movement of the stages 122A, 122B isprovided by respective x-axis position detection systems. Specifically,the x-axis position detection system of the left stage 122A comprises agrating 130A, connected to the stage, and an encoder or grating positiondetector 132A, which is connected to the system frame 110.

The x-axis and y-axis positional control of each of the left and rightstages 122A, 122B, and thus the left and right jaws 120A, 120B, occursunder the control of a controller 210. Specifically, a signalconditioning/sampling circuit 214 receives the position encoder signalsfrom each of the encoders for the x-axis and y-axis position detectionsystems for each of the stages. The signal conditioning/sampling circuit214 then provides the responses from each of the position detectionsystems to the controller 210, which then drives or controls themovement of the stages via the x- and y-axis actuator systems for eachof these stages 122A, 122B via the amplifier bank 200. As a result, thejaws 120A, 120B can be independently positioned to manipulate theoptical component 110 in the x- and y-axis. Z-axis control of theposition of the optical component 10 on the substrate or bench 12 isprovided by the positional control of the z-axis stage 112 by thecontroller. In the preferred embodiment an optical encoder/gratingsystem in combination with an actuator system 113 is used to detect theposition of the z-axis stage.

In some applications of the alignment system 100, a force feedbackscheme is used to drive the stages. This is common in applications inwhich the optical structures are already attached to the substrate butmust be deformed in order to achieve alignment. It is also preferablewhere “slop” or excessive play is present due to deformation in themechanical connection between the optical component 10 and the system100. The play prevents accurate positioning of the optical componentrelative to the substrate based on stage positioning alone due todeformation of the jaws, stages, and substrate-to-z-axis stageconnection.

Specifically, in the force feedback mode of operation, a desiredposition of the optical component relative to the substrate isdetermined in an active alignment search process. The force exerted onthe component to reach this desired position is then recorded along withthe position information from the encoders. Detection of this force ispossible by monitoring the drive current to the voice coils incombination with the low stiction interface between the stages and thesystem frame.

In some applications, this force, rather than the position of thestages, is used to control subsequent optical deformation steps in whichthe stage are driven such that the recorded force is exceeded in orderto initiate plastic deformation of the structure such that the structurereturns to the desired position when force is removed.

In other applications, once the desired position is determined, force isremoved and the optical component is allowed to settle to its positionwhen no external, i.e., force from alignment system 100, is exerted.This initial zero-force position is recorded. Then, a force vector iscalculated that will deform the component such that the component willbe in the determined desired position with no force exert on thecomponent. The component is then deformed accordingly. Subsequentiterations may be implemented to further perfect the component positionthrough its deformation.

In some implementations, it is necessary to heat the optical component10 as it is connected, or after it has been connected, to the bench orsubstrate 12. This can be accomplished through resistive heating. Onedrawback associated with this technique is that wire connections to thestages 122A, 122B are required. These wires can add undesirable biasforces that act on the stages 122.

In the preferred embodiment, a laser system 220 is provided under thecontrol of the controller 210. This laser system generates two beams222, which are respectively focused on the left and right jaws 120A,120B. By controlling the absorption characteristics of the jaws, theradiation from the laser 220 is used to selectively heat the jaws to,for example, heat the optical component 10 to solder bond it to thesubstrate or bench 12.

In some implementations, it is also necessary to heat the bench 12 toeffect this solder bonding. This is accomplished by heating the bench byeither laser heating, a resistive heating technique, or reverse biasingthe module's thermoelectric cooler.

In other embodiments, the bench and/or optical component are inductivelyheated.

In one embodiment the temperature of the optical component 10 and/or thejaws 120A, 120B is detected. This can be accomplished through athermocouple system. In some application, the optical system modulethermocouple is used. Alternatively, a non-contact temperature detectionmethod is used. Specifically, an optical detector is placed in proximityto the optical component on the system frame 110 to detect black bodyradiation from the jaws 120A, 120B and component 10 to thereby providetemperature feedback to the controller 210.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

1. An optical component alignment process, comprising: engaging anoptical component with a first jaw; engaging the optical component witha second jaw; actuating the first and second jaws to move the opticalcomponent along an x- and y-axis to position the optical componentrelative to an optical bench that supports the optical component in anoptical systme provided on the bench.
 2. A process as claimed in claim1, further comprising: first and second opposed jaws for cooperativelyengaging an optical component; detecting an x-axis position of the firstjaw; detecting a y-axis position of the first jaw; an x-axis position ofthe second jaw; detecting a y-axis position of the second jaw.
 3. Aprocess as claimed in claim 1, further comprising heating at least oneof the first and second jaws and thereby an optical component held bythe jaws.
 4. A process as claimed in claim 1, further comprising heatingat least one of the first and second jaws with a laser device thatirradiates at least one of the jaws.
 5. A process as claimed in claim 1,further comprising heating at least one of the first and second jaws andthereby the optical component held by the jaws to a solder meltingtemperature.
 6. A process as claimed in claim 1, further comprisingdriving first x-axis actuator of the first jaw, a first y-axis actuatorof the first jaw, a second x-axis actuator of the second jaw, and asecond y-axis actuator of the second jaw in response to positioninformation from each of a first x-axis position detection system forthe first jaw, the first y-axis position detection system for the firstjaw, a second x-axis position detection system for the second jaw, and asecond y-axis position for the second jaw.
 7. A process as claimed inclaim 1, wherein the jaws extend downward to engage an optical componentfrom above.
 8. A process as claimed in claim 1, wherein the step ofactuating the first and second jaws comprises driving a voice coilsystem.
 9. A process as claimed in claim 1, further comprising detectingpositions of the first jaw and the second jaw with optical encoders andgratings.
 10. A process as claimed in claim 1, further comprisingpositioning the bench in a direction that is at least partiallyorthogonal to the x-axis and the y-axis.